Charged particle beam systems are used in a variety of applications, including the manufacturing, repair, and inspection of miniature devices, such as integrated circuits, magnetic recording heads, and photolithography masks. Examples of charged particle beam systems include focused ion beam (FIB) systems, which produce beams of focused ions, electron microscopes (SEMs, STEMs, and TEMs), which produce beams of electrons, and dual-beam systems, which include subsystems for generating both focused ion and electron beams.
Charged particle beam systems are frequently used in machining applications where it is desired to remove material from a workpiece with microscale and/or nanoscale precision. In the case of a FIB system, material removal can be carried out by a mechanism known as sputtering, in which highly energetic ions of the ion beam bombard the workpiece, causing particles to be locally ejected from the location on the workpiece surface impacted by the beam.
In some cases, it is desired to additionally expose a workpiece (also referred to as a “sample” or “specimen”) to a beam of light inside the sample chamber of the charged particle beam system. For example, in some machining applications, laser ablation is used to remove material from the workpiece at rates higher than can be achieved using a focused ion beam. As another example, some applications use beams of focused or collimated light alone or in combination with a charged particle beam to trigger or alter the surface chemistry of the workpiece, such as in curing, etching, and deposition operations. U.S. Pat. Pub. No. 2014/0131195, which is assigned to the present Applicant and which is hereby incorporated by reference for all purposes, shows examples of systems that include a laser and a charged particle beam system.
In many applications, it is desired to expose the workpiece under vacuum conditions, thus the sample chamber of the charged particle beam system is typically also a vacuum chamber equipped with pumps for evacuating the chamber. However, the vacuum chamber presents a problem for operators when it is also desired to illuminate the sample with a light beam inside the sample chamber because the vacuum chamber obstructs the operator's field of view (FoV) of the light beam inside the chamber, making it difficult to align the light beam with the position on the sample selected for processing and/or analysis. Because of the operator's inability to visualize the position of the light beam inside the sample chamber, it is difficult to precisely align the beam spot with the sample position, and to precisely set the working distance for the focusing optics of the light beam implementation.
Thus, it would be beneficial to find methods for precisely aligning a light beam with a preselected analysis/processing position on a sample inside the vacuum chamber of a charged particle beam system. It would further be beneficial to provide systems and apparatuses capable of performing such methods.